In a valve mechanism for an internal combustion engine, the camshaft rotates in conjunction with the crankshaft when the crankshaft rotates. Rotation of the cam fixed to the camshaft lifts and opens the engine valve.
A valve mechanism for an internal combustion engine described in Patent Document 1 includes a lash adjuster for automatically adjusting the valve clearance of an engine valve, as illustrated in FIG. 10 of the document. The valve mechanism also includes a lost motion mechanism for maintaining the engine valve in a closed state independently from rotation of the cam.
The lost motion mechanism includes a lash adjuster, a housing shaped like a cylinder having a closed end for accommodating the lash adjuster, and a spring arranged in the housing to urge the lash adjuster toward the exterior. The housing and the body of the lash adjuster each have a hole. A lock pin is provided to extend through the holes to engage the housing and the lash adjuster with each other. A spring is provided to cause the lock pin to extend through the holes and urge the lock pin in an engagement direction, in which the housing and the lash adjuster become engaged with each other. A supply passage is also arranged to apply hydraulic pressure to an end face of the lock pin in the opposite direction to the engagement direction. A switch valve is arranged in the supply passage to switch supply modes of the hydraulic pressure.
Also, there is a control device for a valve mechanism that holds the engine valves of some or all of the cylinders of an engine in a (fully) closed state to stop intake and exhaust and stops fuel injection, thereby deactivating the cylinders.
In the above-described valve mechanism for an internal combustion engine, to perform cylinder deactivation, the switch valve applies hydraulic pressure to the end face of the lock pin through the supply passage to cancel the engagement state between the housing and the lash adjuster. This allows the lost motion mechanism to contract when the lost motion mechanism receives drive force from the cam. The lift amount of each engine valve is thus absorbed such that the engine valve is maintained in a closed state.